Cadillac DeVille 1985 to 2005 including:1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, 2003 deville, Check coolant level warning, though resevoir is full in Past Cadillac Vehicle Discussion; I just purchased the car and didn't know if it was the sensor or if the sensor can tell if ...

The sensor isn't calculating your mixture, it measures the actual low coolant level on the system.

The level sensor sometimes gets stuck. Tap the tank gently (especially around the sensor/electrical connector area) to try to free up the sensor. If no luck, partially drain the coolant and take the reservoir off, wash the inside throughly with garden hose, shake the sensor area, and put it back.

I had the same issue with mine last week and as said in an earlier post, try removing the tank and washing it out, only I used some dish soap and warm water and shake vigorously and flush with clean water. It worked for me. You can't but the sensor by itself, you have to purchase the whole surge tank, $130 from the dealer in Canada.

Well before I was able to post on here and get a reply I checked the coolant with a tester and it showed to be a bit below a 50/50 mix so i pulled maybe half a gallon out of the resevoir and replaced with Dex-cool. Nothing happened for a day or so, but then yesterday it no longer gives the check coolant warning. So hopefully it was just a stuck float and the new fluid and moving around got it going again.

The sensor isn't calculating your mixture, it measures the actual low coolant level on the system.

The level sensor sometimes gets stuck. Tap the tank gently (especially around the sensor/electrical connector area) to try to free up the sensor. If no luck, partially drain the coolant and take the reservoir off, wash the inside throughly with garden hose, shake the sensor area, and put it back.

Or you can just replace the reservoir.

WOW!!!! I tapped (with a hammer........ :~) ) the surge tank several times around the sensor and voila!!! The low coolant level warning has stopped. Thanks for the great idea!!!!!

BTW, I have a 2003 DTS. I just got done doing a coolant crossover reseal. OWWWWW!!!!!!! That was a long tough job. I am not sure I would have done it if I knew how long it would take.

Mine gets stuck every time the coolant is drained. Gently tapping at the tank always works. This time I am thinking to flush inside of the surge tank with garden hose though. When you are tapping on it, do not use brutal force though - the surge tank might crack.